Weapons and other evidence recovered from the gunman in Friday's deadly shooting rampage that left five people dead in Santa Monica, Calif., are displayed Saturday in Santa Monica. (AP Photo/Tami Abdollah)

SANTA MONICA, Calif. — A woman who was critically wounded in the Santa Monica shooting rampage died Sunday, bringing the total number of victims killed by the gunman to five.

Marcela Franco, 26, died of her injuries at Ronald Reagan UCLA Medical Center, according to Santa Monica College spokeswoman Tricia Ramos.

Franco had been a passenger in a Ford Explorer driven by her father, campus employee Carlos Navarro Franco, 68, who also was killed in the attack.

Investigators trying to determine why the gunman planned the shooting spree were focusing on a deadly act of domestic violence that touched off the mayhem.

The heavily armed man's attack against his own family led to Friday's violence in Santa Monica streets, lasting just a matter of minutes until he was shot to death in a chaotic scene at a college library by police.

Investigators were looking at family connections to find a motive because the killer's father and brother were the first victims, an official briefed on the probe who requested anonymity because he wasn't authorized to speak publicly told The Associated Press.

The killer, who died a day shy of his 24th birthday, was connected to a home that went up in flames after the first shootings, said police Chief Jacqueline Seabrooks. She refused to elaborate or name the suspect because a surviving family member was out of the country and couldn't immediately be notified.

Standing next to the weapons and ammo found at multiple crime scenes, Seabrooks said at a Saturday news conference that the "cowardly murderer" planned the attack and was capable of firing 1,300 rounds.